A major geomagnetic storm is in progress following the impact of a CME on August 5th around 1800 UT. Sky watchers at all latitudes should be alert for auroras after nightfall. Tip: the best hours for aurora sightings are usually around local midnight.

Analysts at the Goddard Space Weather Lab say that the CME impact may have strongly compressed Earth's magnetic field, directly exposing satellites in geosynchronous orbit to solar wind plasma. Stay tuned for updates on this aspect of the storm.

The arriving CME left the sun on August 4th, propelled by an M9.3-category eruption in the magnetic canopy of sunspot 1261. Click on the image to view a movie of the expanding cloud recorded by the Solar and Heliospheric Observatory: